Chirality control by the aid of 2,2-dimethyloxazolidine chiral auxiliaries. Highly 1,4-chiral inductive asymmetric alkylations of amide enolates

Article abstract of DOI:10.1016/0040-4020(95)00624-H

The propanamide and methoxyacetamide derivatives of (S)-4-benzyl-2,2,5,5-tetramethyloxazolidine, a new chirality controlling auxiliary based on the restricted rotation around amide bond, generate chiral lithium Z-enolates by lithiation. They undergo highly lk-1,4- and ul-1,4-inductive alkylations with a variety of alkylating reagents, respectively. The diastereotopic face participated in the reactions is that remote from the 4-shielding substituent of oxazolidine in the syn-conformations. Coplanarity between the enolate double bond and the oxazolidine plane in the transition state can be a major factor for the observed excellent selectivities.